The present invention is directed generally to an automatic distance-control method and system for motor vehicles.
In conventional vehicle distance-control systems concerned with maintaining a safe distance between a controlled or following vehicle and a lead vehicle (such as, for example, distance-control systems of the type described in DE 44 37 678 A1 and DE 199 51 423 A1), a measuring device acquires information about the distance from the controlled or following vehicle to the lead vehicle and uses the information to control the speed of the controlled vehicle such that the distance to the lead vehicle does not become shorter than a predefined set distance or a speed-dependent set distance. Such speed regulation can be achieved by intervention of a distance-control device in the brake system or engine controller. Typically, in such conventional systems, the maximum deceleration possible is limited to about 2 m/s2.
In situations in which this limited deceleration is not sufficient to prevent critical close approach, a collision can be avoided only if the driver actuates the brakes by depressing the brake pedal quickly enough and far enough. Tests have shown, however, that in some cases drivers faced with emergency situations do not depress the brake pedal fully and thus do not utilize the full braking force available. These tests have led to the development of devices known as brake assistants. A brake assistant, however, can help only if the driver recognizes the danger situation in time.
EP 09 186 73 B 1 describes a brake system having a brake-actuating device, in particular a brake pedal, provided with a first sensor device for sensing the position and change of position of the driver's foot located in the area of the brake pedal above or on the brake pedal, a second sensor device for sensing a force exerted by the foot on the brake pedal, and a third sensor device for sensing measured values describing a danger of collision of the following vehicle with a lead vehicle. Those measured values are the distance to the lead vehicle, the change in distance to the lead vehicle per unit time, the speed of the controlled vehicle and a predefined time that describes the desired safety time until a collision event. A first arithmetic unit that determines a first brake pressure to be activated on the basis of the output values of the first sensor device is allocated to the first sensor device. A second arithmetic unit that determines a second brake pressure to be activated on the basis of the output values of the second sensor device is allocated to the second sensor device. A third arithmetic unit that determines a third brake pressure to be activated on the basis of the measured values of the third sensor device is allocated to the third sensor device. From the output variables of the three arithmetic units, a coordinating unit determines a coordinated pressure value to be transmitted to a brake pressure generator for appropriately increasing the brake pressure.
It is desired to provide an improved automatic vehicle distance-control method and system that can avoid the danger of collision even in critical situations in which the maximum deceleration attainable by the distance-control system is insufficient to prevent the danger of collision.